Light emitting module and planar light source

ABSTRACT

A light emitting module includes: a light guide member including: an emission region defined by a sectioning groove, a light source placement part located in the emission region, and a light adjusting hole that, in a schematic top view, is located between the sectioning groove and the light source placement part; and a light source disposed in the light source placement part. A refractive index of an inside of the light adjusting hole is lower than a refractive index of the light guide member. In the schematic top view, the light adjusting hole is positioned to intersect with a first straight line connecting a center of the light source and a farthest point in the sectioning groove, the farthest point being farthest from the center of the light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2020-019418, filed on Feb. 7, 2020, and Japanese Patent Application No.2020-169826, filed on Oct. 7, 2020, the disclosures of which are herebyincorporated by reference in their entireties.

BACKGROUND

The present disclosure relates to light emitting modules and planarlight sources.

Planar light sources that employ light sources and light guide membershave been used as backlights for liquid crystal displays. For planarlight sources, techniques for sectioning an emission face into multipleemission regions and controlling the luminance per emission region havebeen developed. See, for example, Japanese Patent Publication No.2008-59786. There is a need to reduce luminance non-uniformity in eachemission region.

SUMMARY

One of the objects of certain embodiments of the present invention is toprovide a light emitting module and a planar light source in whichluminance non-uniformity in emission regions is reduced.

According to one embodiment, a light emitting module includes a lightguide member and a light source. The light guide member has an emissionregion defined by a sectioning groove, a light source placement partprovided in the emission region, and a light adjusting hole providedbetween the sectioning groove and the light source placement part in aschematic top view. The light source is disposed in the light sourceplacement part. The refractive index of an inside of the light adjustinghole is lower than a refractive index of the light guide member. Thelight adjusting hole is positioned to intersect with a first straightline connecting a center of the light source and a farthest point in thesectioning groove, the farthest point being farthest from the center ofthe light source, in the schematic top view. The light adjusting holehas a first lateral face located closer to the light source and a secondlateral face located opposite side form the first lateral face. At leastone of normal lines to the first lateral face or at least one of normallines to the second lateral face is oblique to a first direction beingparallel to the first straight line. A width of the light adjusting holein the first direction at a position on the first straight line issmaller than a width of the light adjusting hole in the first directionat a position distant from the first straight line.

According to another embodiment, a planar light source includes thelight emitting module described above and a wiring substrate. The lightguide member is disposed on the wiring substrate. The light source ismounted on the wiring substrate.

According to the embodiments, a light emitting module and a planar lightsource in which luminance non-uniformity in emission regions can beprovided is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of a planar light source according to afirst embodiment.

FIG. 2 is a schematic top view of an emission region of the planar lightsource according to the first embodiment.

FIG. 3 is a schematic cross-sectional view of the planar light sourceaccording to the first embodiment taken along line III-III in FIG. 1.

FIG. 4 is a schematic top view of an emission region of a planar lightsource according to a second embodiment.

FIG. 5 is a schematic top view of an emission region of a planar lightsource according to a third embodiment.

FIG. 6 is a schematic top view of an emission region of a planar lightsource according to a fourth embodiment.

FIG. 7 is a schematic top view of an emission region of a planar lightsource according to a fifth embodiment.

FIG. 8 is a schematic cross-sectional view of a planar light sourceaccording to a first variation.

FIG. 9 is a schematic cross-sectional view of a planar light sourceaccording to a second variation.

FIG. 10 is a schematic cross-sectional view of a planar light sourceaccording to a third variation.

FIG. 11 is a schematic cross-sectional view of a planar light sourceaccording to a fourth variation.

FIG. 12 is a schematic cross-sectional view of a light emitting moduleaccording to a fifth variation.

FIG. 13A is a schematic cross-sectional view of a light source accordingto a sixth variation.

FIG. 13B is a schematic cross-sectional view of a light source accordingto a seventh variation.

FIG. 13C is a schematic cross-sectional view of a light source accordingto an eighth variation.

FIG. 14A is a schematic cross-sectional view of a light source accordingto a ninth variation.

FIG. 14B is a schematic cross-sectional view of a light source accordingto a tenth variation.

FIG. 14C is a schematic cross-sectional view of a light source accordingto an eleventh variation.

EMBODIMENTS First Embodiment

A first embodiment will be explained first.

FIG. 1 is a schematic top view of a planar light source according to theembodiment.

FIG. 2 is a schematic top view of an emission region of the planar lightsource according to the embodiment.

FIG. 3 is a cross-sectional view of the planar light source according tothe embodiment taken along line III-III in FIG. 1.

As shown in FIG. 1 to FIG. 3, the planar light source 1 according to thepresent embodiment has a wiring substrate 200, and a light emittingmodule 100 is disposed on the wiring substrate 200. In the lightemitting module 100, a light guide member 20 and light sources 30 aredisposed. The light guide member 20 is disposed on the wiring substrate200, and the light sources 30 are mounted on the wiring substrate 200.

In the wiring substrate 200, a wiring layer 202 and a connection layer203 that electrically connects the wiring layer 202 and the lightsources 30 are provided in an insulating base material 201. In FIG. 3,only one wiring layer 202 is shown, but multiple wiring layers 202 canbe disposed. An adhesive sheet 205 and a light reflecting sheet 206 aredisposed between the wiring substrate 200 and the light guide member 20.The adhesive sheet 205 adheres the wiring substrate 200 and the lightreflecting sheet 206. The light reflecting sheet 206 reflects a portionof the light emitted from a light source 30.

For the light reflecting sheet 206, a resin sheet containing a largenumber of air bubbles (e.g., foamed resin sheet), a resin sheetcontaining a light diffusing material, or the like can be used. For theresin used as the light reflecting sheet 206, a thermoplastic resin,such as an acrylic resin, polycarbonate resin, cyclic polyolefin resin,polyethylene terephthalate resin, or polyester resin, or a thermosettingresin, such as an epoxy resin or silicone resin, can be used. For thelight diffusing material, any known appropriate material, such astitanium oxide, silica, alumina, zinc oxide, or glass, can be used.

On the upper face of the wiring substrate 200, a light reflecting layerhaving light reflectivity for the light emitted from the light sources30 can further be disposed, and in this case, the adhesive layer 205 isadhered to the light reflecting layer. Alternatively, the lightreflecting layer can be disposed between the light guide member 20described later and the light reflecting sheet 206, for example, on theupper face of the light reflecting sheet 206. This allows the lightreflecting layer to scatter a portion of the light that is emitted fromthe light sources 30 and propagates in the light guide member 20,thereby facilitating the extraction of light from the upper face of thelight guide member 20. Such a light reflecting layer can have a film ordot shape. The light reflecting layer can extend into the light sourceplacement parts 22 of the light guide member 20 described later in theschematic top view. Preferably, the light reflecting layer is extendedto the positions that overlap the light sources 30 in the schematic topview, i.e., between the light sources 30 and the wiring substrate 200.This can hinder the wiring substrate 200 from absorbing a portion of thelight emitted from the light sources 30, thereby moderating theluminance decline around the light sources 30.

For the light reflecting layer, for example, a resin containing anyknown appropriate light diffusing material, such as titanium oxide,silica, alumina, zinc oxide, or glass, can be used. For the resin usedas the light reflecting layer, similarly to that used as the lightreflecting sheet 206, a thermoplastic or thermosetting resin, forexample, can be used. For the resin used as the light reflecting layer,a UV curable resin can alternatively be used.

The light guide member 20 is formed of a light transmissive material,and is plate shaped, for example. For the material used as the lightguide member 20, for example, a thermoplastic resin, such as an acrylicresin, polycarbonate resin, cyclic polyolefin resin, polyethyleneterephthalate resin, or polyester resin, a thermosetting resin, such asan epoxy resin or silicone resin, or glass can be used. In the lightguide member 20, sectioning grooves 21, and emission regions R definedby the sectioning grooves 21(i.e., the sectioning grooves 21 section theemission regions R), light source placement parts 22 positioned in theemission regions R, and light adjusting holes 23 each provided betweenthe light source placement parts 22 and corresponding one of thesectioning grooves 21 in the schematic top view are formed. Thethickness of the light guide member 20 is, for example, preferably 200μm to 800 μm.

In the present disclosure, for the purpose of explanation, an XYZorthogonal coordinate system is employed. The direction in which thewiring substrate 200 and the light guide member 20 are layered isdenoted as the “Z direction” and the directions in which the emissionregions R spread are denoted as the “X direction” and the “Y direction.”With respect to the Z direction, the direction from the wiring substrate200 to the light guide member 20 will also be denoted as the “upwarddirection” and the opposite direction will also be denoted as the“downward direction.” These expressions, however, are used for the sakeof convenience, and have nothing to do with the direction of gravity.Viewing of an object from the upper side will be expressed as “in theschematic top view.”

In the schematic top view, the sectioning grooves 21 form a latticeshape extending in the X direction and the Y direction, individuallysurrounding the emission regions R. The formation of the sectioninggrooves 21 is not limited to a lattice, as long as they can opticallydivide the emission regions R to a practically sufficient extent. Forexample, the sectioning grooves do not have to be provided at thelattice points. This allows the light from adjacent emission regions Rto be collected in the regions including no sectioning groove, therebyinhibiting the corners of the emission regions R from becoming lessluminous. The explanation will be given below using a single emissionregion R, but similarly applies to the other emission regions R.

The width of a sectioning groove 21, for example, can be set to about 5%at most of the width of an emission region R. In the case of disposingthe sectioning member 21 a described later in the sectioning groove 21,it is preferable to set the width of the sectioning groove 21 to make iteasy to dispose the sectioning member 21 a. The sectioning groove 21 canoccupy any appropriate percentage of the light guide member 20 in thethickness direction (Z direction). For example, in the case of reducinglight leakage between adjacent emission regions R, the sectioning groove21 preferably occupies at least 50% of the thickness of the light guidemember 20, more preferably at least 70%, particularly preferably atleast 90%.

As will be explained later with reference to variations of theembodiment, each sectioning groove 21 can be formed on the upper face 20a or the lower face 20 b of the light guide member 20, formed to passthrough the light guide member 20 in the Z direction, formed as a shapein which a through groove is partially closed, or as a hollow space notreaching the upper face 20 a or the lower face 20 b of the light guidemember 20. A hollow sectioning groove 21 can be formed, for example, byadhering together a light guide plate whose upper face has a groove anda light guide plate whose lower face has a groove by using a lighttransmissive adhesive sheet. The same material as that used for thelight guide member 20 is preferably used for such an adhesive sheet soas to reduce a possibility that any interface between the layers iscreated. In the present embodiment, for example, each sectioning groove21 is formed on the upper face 20 a of the light guide member 20.

The inside of each sectioning groove 21 can be an air layer, or includea sectioning member 21 a containing a light reflecting material. For thelight reflecting material, for example, a metal or a resin containing alight diffusing material can be used. For the resin used as the lightreflecting material, a thermoplastic resin, such as an acrylic resin,polycarbonate resin, cyclic polyolefin resin, polyethylene terephthalateresin, or polyester resin, or a thermosetting resin, such as an epoxyresin or silicone resin, can be used. For the light diffusing material,any known appropriate material, such as titanium oxide, silica, alumina,zinc oxide, or glass can be used. For the metal used as the lightreflecting material, for example, platinum (Pt), silver (Ag), rhodium(Rh), or aluminum (Al) can be used. Each sectioning member 21 a can beformed as a layer along the inner face of a sectioning groove 21, or canfill the sectioning groove 21 in whole or part. The upper part of thesectioning members 21 a can protrude higher than the upper face 20 a ofthe light guide member 20. In the present embodiment, for example, eachsectioning member 21 a in the form of a layer is disposed on the innerfaces of the sectioning groove 21.

A light source placement part 22 is a space in which a light source 30is disposed. In other words, the light source 30 is disposed in thelight source placement part 22. As will be explained later withreference to variations of the embodiment, a light source placement part22 can be a through hole passing through the light guide member 20 inthe Z direction, or a recessed part formed on the lower face 20 b of thelight guide member 20. In the present embodiment, the shape of the lightsource placement part 22 is a circle in the schematic top view, but canbe, for example, an ellipse or a polygon, such as a triangle,quadrilateral, hexagon, or octagon.

In the present embodiment, for example, each light source placement part22 is a through hole. A first light transmissive member 25 is providedin the light source placement part 22 so as to embed the light source 30disposed therein. For the first light transmissive member 25, forexample, a light transmissive resin material can be used. For the resinmaterial, similarly to the light guide member 20, a thermoplastic resinor thermosetting resin can be used.

A first light adjusting member 26 is provided on the first lighttransmissive member 25. The first light adjusting member 26 reflects aportion while transmitting a portion of the light emitted from the lightsource 30 that transmitted through the first light transmissive member25. The first light adjusting member 26 can be formed with, for example,a resin material containing a light diffusing material, or a metalmaterial. For example, for the resin material, a silicone resin, epoxyresin, or a resin combining these can be used. For the light diffusingmaterial, any known appropriate material, such as titanium oxide,silica, alumina, zinc oxide, or glass can be used. A dielectricmultilayer film can alternatively be used for the first light adjustingmember 26. In the present embodiment, for example, the first lightadjusting member 26 is disposed in the form of a film, but can bedisposed as dots. Moreover, the first light adjusting member 26 in thepresent embodiment covers the entire upper face of the first lighttransmissive member 25 in the schematic top view, but a portion of theupper face of the first light transmissive member 25 can be exposed fromthe first light adjusting member 26.

A first light reflecting member 27 in the form of a film is disposed atthe bottom of each light source placement part 22, i.e., under the firstlight transmissive member 25. The first light reflecting member 27 isformed with a light reflecting material, such as a metal or a resincontaining a light diffusing material, similarly to the light reflectingmaterial contained in the sectioning member 21 a.

Instead of the first light reflecting member 27, the light reflectingsheet 206 on the wiring substrate 200 can be extended into the lightsource placement part 22 of the light guide member 20 in the schematictop view. In this case, preferably, the light reflecting sheet 206 isextended to a position overlapping the light source 30 in the schematictop view, i.e., between the light source 30 and the wiring substrate200. This can hinder the wiring substrate 200 from absorbing a portionof the light emitted from the light sources 30, thereby moderating theluminance decline around the light sources 30.

The light source 30 can be a light emitting element by itself, or astructure body in which a light emitting element and an optical membersuch as a wavelength conversion member are combined. As will beexplained later with reference to variations of the embodiment, thelight source 30 can take a variety of forms.

In the present embodiment, each light source 30 includes a lightemitting element 31, a cover member 33, a second light transmissivemember 34, and a second light adjusting member 35. The light emittingelement 31 includes at least a semiconductor structure body and a pairof positive and negative electrodes. The light emitting element 31 is,for example, a light emitting diode (LED), and emits, for example, bluelight. The semiconductor structure body can include, for example,In_(x)Al_(y)Ga_(1-x-y)N (0≤x, 0≤y, x+y≤1). The light emitting element 31has a first face 31 a on which a pair of positive and negativeelectrodes is disposed, and a second face 31 b that opposes the firstface 31 a.

In the semiconductor structure body of the light emitting element 31, alight emitting diode structure body is achieved by stacking at least ap-type semiconductor layer, an emission layer, and an n-typesemiconductor layer, for example. The emission layer can have a singleactive layer, such as a double heterostructure body or a single quantumwell (SQW) structure body, or can have a group of active layers such asa multi-quantum well (MQW) structure body. The emission layer can emitvisible light or ultraviolet light. Examples of visible light include atleast blue light to red light. A semiconductor structure body thatincludes such an emission layer can include, for example,In_(x)Al_(y)Ga_(1-x-y)N (0≤x, 0≤y, x+y≤1).

The light emitting element 31 can include two or more emission layers inthe semiconductor structure body. For example, the semiconductorstructure body can be one that includes two or more emission layersbetween an n-type semiconductor layer and a p-type semiconductor layer,or one formed by repeating two or more structure bodies eachsuccessively stacking an n-type semiconductor layer, an emission layer,and a p-type semiconductor layer. Two or more emission layers caninclude those that emit light of different colors or the same color. Thesame emission color can be a range of emission colors that can be deemedas the same for the purpose of use. For example, there can be variationof about several nanometers in the dominant wavelength of each emissioncolor. A combination of emission colors can be suitably selected.Examples of color combinations in the case of two emission layersinclude blue light and blue light, green light and green light, redlight and red light, ultraviolet light and ultraviolet light, blue lightand green light, blue light and red light, green light and red light, orthe like.

The cover member 33 is, for example, a resin material containing a lightdiffusing material, and is disposed in the surrounding of the lower partof the light emitting element 31. Specifically, for the cover member 33,a silicone or epoxy resin containing a light diffusing material, such astitanium oxide, silica, alumina, zinc oxide, or glass can be used. Aplanar light source 1 is provided with a bonding material 40 such assolder. The bonding material 40 connects the pair of positive andnegative electrodes of the light emitting element 31 to the connectionlayer 203 of the wiring substrate 200, but can connect to the wiringlayer 202 without via the connection layer 203.

The second light transmissive member 34 is disposed on the upper partof, around and above the light emitting element 31. The second lighttransmissive member 34 is formed of a light transmissive resin materialthat can contain a phosphor, but does not have to contain. For the resinmaterial used as the second light transmissive member 34, for example,an epoxy resin, silicone resin, or a resin mixing these can be used. Inthe case in which the second light transmissive member 34 contains aphosphor, the second light transmissive member 34 serves as a wavelengthconversion layer.

For the phosphors, yttrium aluminum garnet-based phosphors (e.g.,Y₃(Al,Ga)₅O₁₂:Ce), lutetium aluminum garnet-based phosphors (e.g.,Lu₃(Al,Ga)₅O₁₂:Ce), terbium aluminum garnet-based phosphors (e.g.,Tb₃(Al,Ga)₅O₁₂:Ce), β-SiAlON phosphors (e.g., (Si,Al)₃(O,N)₄:Eu),α-SiAlON phosphors (e.g., Mz(Si,A1)₁₂(O,N)₁₆ where 0<z≤2 and M is anelement selected from the group consisting of Li, Mg, Ca, Y, andlanthanide elements excluding La and Ce), nitride-based phosphors, suchas CASN-based phosphors (e.g., CaAlSiN₃:Eu) or SCASN-based phosphors(e.g., (Sr,Ca)AlSiN₃:Eu), fluoride-based phosphors, such as KSF-basedphosphors (e.g., K₂SiF₆:Mn) or MGF-based phosphors (e.g.,3.5MgO.0.5MgF₂.GeO₂:Mn), or quantum dot phosphors can be used.

The second light transmissive member 34 can contain several types ofphosphors. For example, containing a phosphor that absorbs blue lightand emits yellow light and a phosphor that absorbs blue light and emitsred light allows the light source 30 to emit white light. The secondlight transmissive member 34 can contain a light diffusing material tothe extent not to shield light. The content of the light diffusingmaterial in the second light transmissive member 34 can be adjusted suchthat the transmittance of the second light transmissive member 34 forthe light emitted from the light emitting element 31 is 50% to 99%,preferably 70% to 90%. For the light diffusing material, for example,titanium oxide, silica, alumina, zinc oxide, or glass can be used.

The second light adjusting member 35 is disposed on the upper face ofthe second light transmissive member 34. The second light adjustingmember 35, similarly to the first light adjusting member 26, is formedwith a light reflecting material, such as a metal or a resin materialcontaining a light diffusing material. The second light adjusting member35 reflects a portion and transmits a portion of the light entering fromthe second light transmissive member 34. In the case in which thetransmittance of the second light adjusting member 35 for the lightemitted from the light emitting element 31 is sufficiently low, forexample, 1% to 50%, preferably 3% to 30%, the second light adjustingmember 35 serves as a light shielding film, preventing the luminanceimmediately above the light source 30 from becoming excessively high.

Each light adjusting hole 23, similar to the sectioning grooves 21, canbe formed on the upper face 20 a or the lower face 20 b of the lightguide member 20, formed to pass through the light guide member 20 in theZ direction, formed as a shape in which a through hole is partiallyclosed, or formed as a hollow space not reaching the upper face 20 a orthe lower face 20 b of the light guide member 20. In the presentembodiment, for example, each light adjusting hole 23 is formed on theupper face 20 a of the light guide member 20. In other words, the lightadjusting holes 23 reach the upper face 20 a of the light guide member20, but are positioned apart from the lower face 20 b of the light guidemember 20.

In the present disclosure, the term, “hole,” is a general designationfor a recessed part and a through hole. In other words, a “hole” can bea recessed part that does not pass through the body (e.g., the lightguide member 20) in which it is created, or a through hole that passesthrough the body. Furthermore, the shape of a “hole” is not limited. Inother words, it includes a high aspect ratio shape such as a grooveextending in one direction in the schematic top view, a low aspect ratioshape such as a circular or polygonal shape in the schematic top view,and any other regular or irregular shape therebetween. Moreover, theinternal structure of a “hole” can also be appropriately selected. Inother words, a “hole” includes one having an air layer inside, onehaving a certain member intentionally provided therein, and one in whichan unintended substance has been entered.

In the case of disposing the light transmissive member described laterin each light adjusting hole 23, it is preferable to set the openingwidth of the light adjusting hole 23 such that the light transmissivemember is easily disposed. Each light adjusting hole 23 can occupy anypercentage in the thickness direction of the light guide member 20. Forexample, in the case of increasing the amount of the light emitted fromthe light source 30 that advances towards the corners of the emissionregion R, the light adjusting holes 23 preferably occupy at least 15%,more preferably at least 25%, particularly preferably at least 50% ofthe thickness of the light guide member 20.

The inside of each light adjusting hole 23 can be an air layer, orinclude a light transmissive material disposed therein. In the case inwhich a light transmissive material is disposed inside the lightadjusting hole 23, the refractive index of the light transmissivematerial is preferably lower than the refractive index of the lightguide member 20. Examples of resins for use as the light transmissivematerial include thermoplastic resins, such as an acrylic resin,polycarbonate resin, cyclic polyolefin resin, polyethylene terephthalateresin, or polyester resin, or thermosetting resins, such as an epoxyresin or silicone resin. Moreover, the light transmissive material cancontain a light diffusing material. For the light diffusing material,any known material, such as titanium oxide, silica, alumina, zinc oxide,or glass can be used. The light transmissive material can be disposed inthe form of a layer along the inner face of a light adjusting hole 23,or can fill the light adjusting hole 23. In the present embodiment, forexample, the inside of each light adjusting hole 23 is an air layer.Thus, the refractive index of the inside of each light adjusting hole 23is lower than the refractive index of the light guide member 20.

The planar arrangement of the light adjusting holes 23 will be explainednext.

For the purpose of explanation, an imaginary first straight line L1 andan imaginary second straight line L2 are established in the emissionregion R. A first straight line L1 is a straight line connecting thecenter 30 c of the light source 30 and a farthest point 21 b in thesectioning groove 21 that is farthest from the center 30 c of the lightsource 30, in the schematic top view. In the case in which the shape ofeach emission region R is polygonal in the schematic top view, a firststraight line 1 can be a straight line that connects the center 30 c ofthe light source 30 and a corner of the emission region R. A secondstraight line L2 is a straight line connecting the center 30 c of thelight source 30 and a closest point 21 c in the sectioning groove 21that is closest from the center 30 c of the light source 30, in theschematic top view.

The “center of the light source” is a geometric center in the schematictop view, and in the case in which the shape of the light source 30 isquadrilateral, for example, the center 30 c is the intersection of thediagonal lines of the light source 30. “A farthest point 21 b in thesectioning groove that is farthest from the center of the light source”means a point in the sectioning groove 21 (i.e., sectioning groovesurrounding the light source 30) that is farthest from the center 30 cof the light source 30, where other sectioning grooves 21 surroundingonly other light sources 30 are not taken into consideration. In thecase in which the shape of the emission region R is quadrilateral, afarthest pint 21 b is a corner of the sectioning groove 21. In the casein which the shape of the emission region R is quadrilateral and thecenter 30 c of the light source 30 coincides with the center of theemission region R in the schematic top view, there are four firststraight lines L1 and four second straight lines L2.

In the schematic top view, each light adjusting hole 23 is disposed inthe position to intersect with a first straight line L1. In the presentembodiment, the light adjusting holes 23 are not positioned on anysecond straight line L2. The shape of each emission region R isquadrilateral in the schematic top view, and the light adjusting holes23 are provided such that one light adjusting hole is positioned betweenthe light source 30 and each corner of the emission region R.

In the schematic top view, each light adjusting hole 23 has the shape ofa plano-concave-type concave lens. More specifically, each lightadjusting hole 23 has a first lateral face 23 a positioned closer to thelight source 30 side, and a second lateral face 23 b positioned oppositeto the first lateral face 23 a. The second lateral face 23 b ispositioned closer to a farthest point 21 b of the sectioning groove 21.The first lateral face 23 a is a plane orthogonal to a first straightline L1, and the second lateral face 23 b is a concave face so as to becurved inward of the light adjusting hole 23. The curvature of such asecond lateral face 23 b is, for example, preferably 0.3 to 1.3, morepreferably 0.35 to 1.0.

In the first direction V parallel to a first straight line L1, the widthW1 of a light adjusting hole 23 on the first straight line L1 is smallerthan the width W2 of the light adjusting hole 23 at a position P1distant from the first straight line L1. In other words, W1<W2. Thewidth W1 is, for example, the minimum value of the width of the lightadjusting hole 23 in the first direction V. At least one of the normallines N2 normal to the second lateral face 23 b is oblique to the firstdirection V.

The operation of the planar light source according to the presentembodiment will be explained next.

FIG. 2 shows several examples of optical paths T.

When power is supplied to the light source 30 via the wiring substrate200, the light source 30 emits light. The light emitted from the lightsource 30 is introduced into the light guide member 20 via the firstlight transmissive member 25, and then propagates in the light guidemember 20 while being reflected by the upper face 20 a and the lowerface 20 b of the light guide member 20.

A portion of the light propagated in the light guide member 20 reachesthe light adjusting holes 23. Because the refractive index of the insideof each light adjusting hole 23 is lower than the refractive index ofthe light guide member 20, and the light adjusting holes 23 are concavelens shaped, an optical action similar to that of a regular convex lensresults in the light adjusting holes 23 thereby converging the lightthat passed through the light adjusting holes 23. Accordingly, the lightthat passed through the light adjusting holes 23 is refracted towardsthe first straight lines L1 to be collected in the vicinities of thecorners of the emission region R. This, as a result, increases thebrightness in the corners of the emission region R, thereby reducingluminance non-uniformity in the emission region R. Once the lightreaches the sectioning groove 21, further propagation is obstructed bythe sectioning groove 21. This may suppress the light from leaking intoadjacent emission regions R.

The effect of the embodiment will be explained next.

In the present embodiment, sectioning grooves 21 are formed in the lightguide member 20 to section the emission face of the light emittingmodule 100 into a plurality of emission regions R. In the emissionregions R, light source placement parts 22 are respectively formed wherelight sources 30 are respectively disposed. The majority of the lightemitted from the light sources 30 exits through the upper face 20 of thelight guide member 20 before reaching the sectioning grooves 21.Accordingly, the majority of the light emitted by a light source 30exits the light emitting module 100 from the emission region R in whichthe light source 30 is disposed. This makes it possible to control theluminous intensity per emission region R. As a result, a high contrastimage can be displayed when a planar light source according to theembodiment is used as a light source for a liquid crystal display, forexample.

In the present embodiment, moreover, light can be refracted using thelight adjusting holes 23. Because the corners of the emission regions Rare distant from the light sources 30, the corners of the emissionregions R can easily be less luminous in the absence of light adjustingholes 23. Accordingly, in the present embodiment, light adjusting holes23 are formed in the positions to intersect with the first straightlines L1. Accordingly, at least one portion of the light propagatingnear the first straight lines L1 is converged in the vicinities of thecorners of the emission region R by the light adjusting holes 23. This,as a result, can increase the brightness in the corners of the emissionregions R, thereby reducing luminance non-uniformity in each emissionregion R.

Second Embodiment

A second embodiment will be explained next.

FIG. 4 is a schematic top view of one emission region of a planar lightsource according to the embodiment.

As shown in FIG. 4, in the planar light source 2 according to thepresent embodiment, each light adjusting hole 23 is also concave lensshaped in the schematic top view. As compared to the first embodiment,the orientation of the light adjusting holes 23 is reversed. In otherwords, the first lateral face 23 a of each light adjusting hole 23 is aconcave face so as to be curved inward of the light adjusting hole 23.The second lateral face 23 b of each light adjusting hole 23 is a flatface orthogonal to a first straight line L1.

In the schematic top view, each light adjusting hole 23 intersects witha first straight line L1 and is positioned apart from second straightlines L2. In the first direction V parallel to a first straight line L1,the width W1 of a light adjusting hole 23 on the first straight line L1is smaller than the width W2 of the light adjusting hole 23 at aposition P1 distant from the first straight line L1. The width W1 is,for example, the minimum value of the width of the light adjusting hole23 in the first direction V Furthermore, at least one of the normallines N1 normal to the first lateral face 23 a are oblique to the firstdirection V. The present embodiment can also achieve a similar effect tothat achieved by the first embodiment. The other elements not describedabove, the operation, and the effect of the present embodiment aresimilar to those of the first embodiment.

Third Embodiment

A third embodiment will be explained next.

FIG. 5 is a schematic top view of one emission region of a planar lightsource according to the embodiment.

As shown in FIG. 5, the planar light source 3 according to the presentembodiment is different from the planar light source 1 according to thefirst embodiment in that the first lateral face 23 a of each lightadjusting hole 23 is a convex face so as to be curved outwardlyprotruding from the light adjusting hole 23. The curvature of the firstlateral face 23 a is smaller than the curvature of the second lateralface 23 b. Accordingly, in the schematic top view, the shape of eachlight adjusting hole 23 is a concave meniscus-type concave lens.

In the schematic top view, each light adjusting hole 23 intersects witha first straight line L1 and is positioned apart from second straightlines L2. In the first direction V parallel to a first straight line L1,the width W1 of a light adjusting hole 23 on the first straight line L1is smaller than the width W2 of the light adjusting hole 23 at aposition P1 distant from the first straight line L1. The width W1 is,for example, the minimum value of the width of the light adjusting hole23 in the first direction V Furthermore, at least one of the normallines N1 normal to the first lateral face 23 a and at least one of thenormal lines N2 normal to the second lateral face 23 b are oblique tothe first direction V. The other elements not described above, theoperation, and the effect of the present embodiment are similar to thoseof the first embodiment.

Fourth Embodiment

A fourth embodiment will be explained next.

FIG. 6 is a schematic top view of one emission region of a planar lightsource according to the embodiment.

As shown in FIG. 6, in the planar light source 4 according to thepresent embodiment, the shape of each light adjusting hole 23 in theschematic top view is a biconcave-type concave lens. In other words,both the first lateral face 23 a and the second lateral face 23 b ofeach light adjusting hole 23 are concave faces so as to be curved inwardof the light adjusting hole 23. The other elements not described above,the operation, and the effect of the present embodiment are similar tothose of the first embodiment.

Fifth Embodiment

A fifth embodiment will be explained next.

FIG. 7 is a schematic top view of one emission region of a planar lightsource according to the embodiment.

As shown in FIG. 7, in the planar light source 5 according to thepresent embodiment, a single light adjusting hole 23 is provided in eachemission region R. In the schematic top view, the shape of the lightadjusting hole 23 is annular, surrounding the light source placementpart 22 in each emission region. In the light adjusting hole 23, concavelens-shaped parts 23 s are provided in the portions that intersect withthe first straight lines L1, and linking parts 23 t are provided in theportions that intersect with the second straight lines L2. In thepresent embodiment, the concave lens-shaped parts 23 s and the linkingparts 23 t are provided in four locations each, which are alternatelyarranged along the circumferential direction of the light adjusting hole23 and integrally formed.

The shape of each concave lens-shaped part 23 s is similar to the shapeof the light adjusting hole 23 explained with reference to the secondembodiment. Accordingly, an optical action similar to that of a regularconcave lens results in each concave lens-shaped part 23 s. On the otherhand, the width of each linking part 23 t is substantially uniform.Accordingly, an optical action does not substantially take place at thelinking parts 23 t. For example, the width in the direction parallel tothe second straight line L2 of a linking part 23 t at the portion thatintersects with a second straight line L2 is smaller than the width inthe first direction of a concave lens-shaped part 23 s at the portionthat intersects with a first straight lien L1 V. The other elements notdescribed above, the operation, and the effect of the present embodimentare similar to those of the first embodiment.

Variations common to the embodiments described above will be explainedbelow.

The first to fourth variations described below are variations related tothe shapes of the sectioning grooves 21, the light source placementparts 22, and the light adjusting holes 23 in the up-down direction. Thefifth variation is an example in which a wiring substrate 200 is notdisposed. The sixth to eleventh variations are variations related to thelight sources 30. The drawings showing the variations below areschematic, in which certain elements might be omitted or simplified asappropriate. The embodiments described above and the variationsdescribed below can be implemented in combination.

First Variation

FIG. 8 is a cross-sectional view of a planar light source according to afirst variation.

As shown in FIG. 8, in the planar light source 11 of this variation, thesectioning groove 21 and the light adjusting holes 23 are formed on theupper face 20 a side of the light guide member 20. In other words, thesectioning groove 21 and the light adjusting holes 23 reach the upperface 20 a of the light guide member 20, but are positioned apart fromthe lower face 20 b.

The sectioning groove 21 is filled with a sectioning member 21 acontaining a light reflecting material, and the inside of the sectioninggroove 21 is entirely buried under the sectioning member 21 a. The lightadjusting holes 23 are filled with a light transmissive member 23 eformed of a light transmissive material such as a transparent resin, andthe inside of each light adjusting hole 23 is entirely buried under thelight transmissive member 23 e. The refractive index of the lighttransmissive member 23 e is lower than the refractive index of the lightguide member 20. The upper edge of the sectioning member 21 a and theupper edges of the light transmissive members 23 e are positioned higherthan the upper face 20 a of the light guide member 20. The light sourcepositing part 22 is a recessed part formed on the lower face 20 b of thelight guide member 20. The light source placement part 22 can beentirely or partially filled with a first light transmissive member 25,or can be an air layer. In this example, both the sectioning groove 21and the light adjusting holes 23 are illustrated such that the distancebetween the inner lateral faces of each sectioning groove 21 and thedistance between the inner lateral faces of each light adjusting hole 23increase towards the top, but the configurations are not limitedthereto. The distance between the inner lateral faces of each sectioninggroove 21 and the distance between the inner lateral faces of each lightadjusting hole 23 can be increased towards the bottom, or remainsubstantially parallel in the Z direction.

Second Variation

FIG. 9 is a cross-sectional view of a planar light source according to asecond variation.

As shown in FIG. 9, in the planar light source 12 of this variation, thesectioning groove 21 and the light adjusting holes 23 are formed on thelower face 20 b of the light guide member 20. In other words, thesectioning groove 21 and the light adjusting holes 23 are positionedapart from the upper face 20 a of the light guide member 20, but reachthe lower face 20 b. The inside of the sectioning groove 21 and thelight adjusting holes 23 are air layers. The light source placement part22 is a recessed part formed on the lower face 20 b of the light guidemember 20. The light source placement part 22 can be entirely orpartially filled with a first light transmissive member 25, or can be anair layer. FIG. 9 shows an example in which the inner lateral faces ofeach sectioning groove 21 and the inner lateral faces of each lightadjusting hole 23 are substantially parallel in the Z direction, howeverthe configurations are not limited thereto. The distance between theinner lateral faces of each sectioning groove 21 and the distancebetween the inner lateral faces of each light adjusting hole 23 can beincreased towards the top or bottom.

Third Variation

FIG. 10 is a cross-sectional view of a planar light source according toa third variation.

As shown in FIG. 10, in the planar light source 13 of this variation,the sectioning groove 21 and the light adjusting holes 23 pass throughthe light guide member 20 in the up-down direction (Z direction). Inother words, the sectioning groove 21 and the light adjusting holes 23reach both the upper face 20 a and the lower face 20 b of the lightguide member 20. The inside of the sectioning groove 21 and the insideof the light adjusting holes 23 are air layers. The sectioning groove 21and the light adjusting holes 23 can be partially closed. The lightsource placement part 22 also passes through the light guide member 20in the up-down direction (Z direction). A first light transmissivemember 25 fills the light source placement part 22. On the first lighttransmissive member 25, a first light adjusting member 26 is disposed.The first light transmissive member 25 and the first light adjustingmember 26 do not have to be provided, or only the first lighttransmissive member 25 can be provided without providing the first lightadjusting member 26. FIG. 10 shows an example in which the inner lateralfaces of each sectioning groove 21 and the inner lateral faces of eachlight adjusting hole 23 that pass through the light guide member 20 aresubstantially parallel in the Z direction, however, the configurationsare not limited thereto. The distance between the inner lateral faces ofeach sectioning groove 21 and the distance between the inner lateralfaces of each light adjusting hole 23 can be increased towards the top,or can be increased toward the bottom.

Fourth Variation

FIG. 11 is a cross-sectional view of a planar light source according toa fourth variation.

As shown in FIG. 11, in the planar light source 14 of this variation,the sectioning groove 21 and the light adjusting holes 23 are formed inthe light guide member 20. In other words, the sectioning grove 21 andthe light adjusting holes 23 are positioned apart from both the upperface 20 a and the lower face 20 b of the light guide member 20. Theinside of the sectioning groove 21 and the inside of the light adjustingholes 23 are air layers. The light source placement part 22 passesthrough the light guide member 20 in the up-down direction (Zdirection).

Such a light guide member 20 can include a lower light guide plate andan upper light guide plate. The upper face of the lower light guideplate is provided with a recessed part that will become the lowerportion of the sectioning groove 21, recessed parts that will become thelower portions of the light adjusting holes 23, and a through hole thatwill become the lower portion of the light source placement part 22. Thelower face of the upper light guide plate is provided with a recessedpart that will become the upper portion of the sectioning groove 21,recessed parts that will become the upper portions of the lightadjusting holes 23, and a through hole that will become the upperportion of the light source placement part 22. Such a light guide member20 can be formed by adhering a lower light guide plate and an upperlight guide plate together. A first light transmissive member 25entirely or partially fills the light source placement part 22. On thefirst light transmissive member 25, a first light adjusting member 26 isprovided.

Fifth Variation

FIG. 12 is a cross-sectional view of a light emitting module accordingto a fifth variation.

As shown in FIG. 12, in the light emitting module 115 of this variation,no wiring substrate 200 is provided. In the light guide member 20, thelight source placement part 22 is a recessed part formed on the lowerface 20 b of the light guide member 20. The light source 30 is disposedin the light source placement part 22, and an affixing member 29 isprovide in the space between the light source 30 and the light guidemember 20 in the light source placement part 22. The affixing member 29is, for example, formed of a light transmissive resin material. Thelight source 30 is fixed to the light guide member 20 via the affixingmember 29.

The sectioning groove 21 is formed on the lower face 20 b of the lightguide member 20, and a sectioning member 21 a is provided insidethereof. The sectioning member 21 a reaches the light source placementpart 22. A pair of wirings 120 is disposed on the lower face of thesectioning member 21 a. The pair of wirings 120 is electricallyconnected to the pair of positive and negative electrodes of the lightemitting element 31 of the light source 30 via a pair of externalelectrode members 210. The light adjusting holes 23 are formed at theupper face 20 a of the light guide member 20. A recessed part 121 iscreated in the region of the upper face 20 a of the light guide member20, the region of the upper face 20 a including the area immediatelyabove the light source placement part 22. A first light adjusting member26 can be provided in the recessed part 121, but does not have to beprovided.

The light emitting module 115 of this variation constructs a planarlight source by being mounted on an external substrate (not shown).Power is supplied to the light source 30 from the external substrate.

Sixth Variation

FIG. 13A is a cross-sectional view of a light source according to asixth variation.

As shown in FIG. 13A, in the light source 30A of this variation, a lightemitting element 31, a cover member 33, and a second light transmissivemember 34 are provided. A pair of external electrode members 210 isconnected to the pair of positive and negative electrodes disposed onthe first face 31 a of the light emitting element 31. The cover member33 is disposed under the first face 31 a of the light emitting element31 around the external electrode members 210. The second lighttransmissive member 34 covers the lateral faces 31 c and the second face31 b of the light emitting element 31. The second light transmissivemember 34 can be a wavelength conversion layer containing a phosphor.

Seventh Variation

FIG. 13B is a cross-sectional view of a light source according to aseventh variation.

As shown in FIG. 13B, the light source 30B of this variation differsfrom the light source 30A of the sixth variation in that the covermember 33 covers the lateral faces 31 c of the light emitting element31, the second light transmissive member 34 is disposed on the secondface 31 b of the light emitting element 31, and a second light adjustingmember 35 is disposed on the second light transmissive member 34. In thecase in which the transmittance of the second light adjusting member 35is sufficiently low, the second light adjusting member 35 serves as alight shielding film.

Eighth Variation

FIG. 13C is a cross-sectional view of a light source according to aneighth variation.

As shown in FIG. 13C, the light source 30C of this variation differsfrom the light source 30B of the seventh variation in that no secondlight adjusting member 35 is provided.

Ninth Variation

FIG. 14A is a cross-sectional view of a light source according to aninth variation.

As shown in FIG. 14A, the light source 30D of this variation differsfrom the light source 30A of the sixth variation in that it does notinclude any cover member 33 or second light transmissive member 34, butincludes a light shielding layer 36. The light shielding layer 36 isdisposed on the second face 31 b of the light emitting element 31. Thelight shielding layer 36 is, for example, a metal layer or a distributedBragg reflector (DBR). The light shielding layer 36 can be formed of aresin containing a light diffusing material.

Tenth Variation

FIG. 14B is a cross-sectional view of a light source according to atenth variation.

As shown in FIG. 14B, the light source 30E of this variation differsfrom the light source 30A of the sixth variation in that a lighttransmissive layer 37 is provided instead of the second lighttransmissive member 34, and a light shielding film 38 is furtherprovided. The light transmissive layer 37 is, for example, formed of alight transmissive resin layer. The light transmissive layer 37, forexample, is substantially from of a phosphor. The light transmissivelayer 37 can contain a light diffusing material. The light shieldingfilm 38 is disposed on the light transmissive layer 37. The lightshielding film 38 is , for example, a metal layer or a distributed Braggreflector. The light shielding film 38 can be formed of a resincontaining a light diffusing material.

Eleventh Variation

FIG. 14C is a cross-sectional view of a light source according to aneleventh variation.

As shown in FIG. 14C, the light source 30F of this variation differsfrom the light source 30E of the tenth variation in that the covermember 33 covers the lateral faces 31 c of the light emitting element31, and the light transmissive layer 37 is disposed on the second face31 b of the light emitting element 31.

In the embodiments and the variations described above, the light guidemember 20 was illustrated as a plate-shaped member, but the light guidemember 20 is not limited to this. The light guide member 20 can be alayer formed to cover the light sources 30. The light guide member 20can have a multilayer structure body or as blocks provided per emissionregion R. Moreover, a light source 30 can have a plurality of lightemitting elements. Furthermore, the shape of each emission region R isnot limited to quadrilateral, and can be polygonal other thanquadrilateral, such as triangular or hexagonal.

What is claimed is:
 1. A light emitting module comprising: a light guidemember comprising: an emission region defined by a sectioning groove, alight source placement part located in the emission region, and a lightadjusting hole that, in a schematic top view, is located between thesectioning groove and the light source placement part; and a lightsource disposed in the light source placement part, wherein: arefractive index of an inside of the light adjusting hole is lower thana refractive index of the light guide member, in the schematic top view,the light adjusting hole is positioned to intersect with a firststraight line connecting a center of the light source and a farthestpoint in the sectioning groove, the farthest point being farthest fromthe center of the light source, the light adjusting hole has a firstlateral face located closer to the light source and a second lateralface located opposite the first lateral face, at least one of normallines to the first lateral face or at least one of normal lines to thesecond lateral face is oblique to a first direction that is parallel tothe first straight line, and a width of the light adjusting hole in thefirst direction at a position on the first straight line is smaller thana width of the light adjusting hole in the first direction at a positiondistant from the first straight line.
 2. The light emitting moduleaccording to claim 1, wherein: in the schematic top view, a shape of theemission region is quadrilateral, and the first straight line connectsthe center of the light source and a corner of the emission region. 3.The light emitting module according to claim 2, wherein: the light guidemember has at least one additional light adjusting hole, and in theschematic top view, the light adjusting hole and the additional lightadjusting hole are respectively located at positions between the lightsource and corners of the emission region.
 4. The light emitting moduleaccording to claim 1, wherein: light emitted from the light source isrefracted in the light adjusting hole.
 5. The light emitting moduleaccording to claim 1, wherein: an air layer is located inside the lightadjusting hole.
 6. The light emitting module according to claim 1,wherein: in the schematic top view, the light adjusting hole is notpositioned on a second straight line that connects the center of thelight source and a closest point in the sectioning groove, the closestpoint being closest from the center of the light source.
 7. The lightemitting module according to claim 1, wherein: in the schematic topview, the second lateral face is concave-shaped so as to be curvedinward of the light adjusting hole.
 8. The light emitting moduleaccording to claim 7, wherein: in the schematic top view, the firstlateral face is convex-shaped so as to be curved outwardly protrudingfrom the light adjusting hole, and a curvature of the first lateral faceis smaller than a curvature of the second lateral face.
 9. The lightemitting module according to claim 7, wherein: the first lateral faceextends in a plane orthogonal to the first straight line.
 10. The lightemitting module according to claim 1, wherein: in the schematic topview, the first lateral face is concave-shaped so as to be curved inwardof the light adjusting hole.
 11. The light emitting module according toclaim 1, wherein: in the schematic top view, the light adjusting hole isconcave lens-shaped.
 12. The light emitting module according to claim 1,wherein: the light adjusting hole reaches the upper face of the lightguide member, but is positioned apart from the lower face of the lightguide member.
 13. The light emitting module according to claim 1,wherein: the light adjusting hole passes through the light guide memberfrom an upper face to a lower face of the light guide member.
 14. Thelight emitting module according to claim 1, further comprising: a lightadjusting member disposed in an area immediately above the light sourceplacement part in an upper face of the light guide member to reflect aportion of light emitted from the light source and transmit a portion ofthe light emitted from the light source.
 15. The light emitting moduleaccording to claim 1, wherein: the light source comprises a lightemitting element, and the light emitting element has a first face onwhich a pair of positive and negative electrodes are formed, and asecond face located opposite the first face.
 16. The light emittingmodule according to claim 15, wherein: the light emitting elementfurther comprises a light shielding layer disposed on the second face.17. The light emitting module according to claim 15, wherein: the lightsource further comprises: a light transmissive layer disposed at leaston the second face of the light emitting element, and a light shieldingfilm disposed on the light transmissive layer.
 18. The light emittingmodule according to claim 15, wherein: the light source furthercomprises a wavelength conversion layer disposed at least on the secondface of the light emitting element.
 19. The light emitting moduleaccording to claim 18, wherein: the light source further comprises alight shielding film disposed on the wavelength conversion layer.
 20. Aplanar light source comprising: a light emitting module according toclaim 1, and a wiring substrate, wherein: the light guide member isdisposed on the wiring substrate, and the light source is mounted on thewiring substrate.